In the latter half of the twentieth century, there began a phenomenon known as the information revolution. While the information revolution is a historical development broader in scope than any one event or machine, no single device has come to represent the information revolution more than the digital electronic computer. The development of computer systems has surely been a revolution. Each year, computer systems grow faster, store more data, and provide more applications to their users. At the same time, the cost of computing resources has consistently declined, so that information which was too expensive to gather, store and process a few years ago, is now economically feasible to manipulate via computer. The reduced cost of information processing drives increasing productivity in a snowballing effect, because product designs, manufacturing processes, resource scheduling, administrative chores, and many other factors, are made more efficient.
Communication at various levels is a necessary ingredient of the information revolution. Not only should people be able to communicate immediately, directly, and without limitations, over long distances (by telephone, radio, etc.), but digital computing devices should also be able to communicate with one another. The reduced cost of computing and the general availability of digital devices has brought an explosion in the volume of information stored in such devices. The volume of information dwarfs the storage capability of any one device, making it desirable to facilitate wide access to information stored among different computer systems. To improve information access, various techniques for allowing computing devices to communicate and exchange information with one another have been developed. Perhaps the most outstanding example of this distributed computing is the World Wide Web (often known simply as the “web”), a collection of resources which are made available throughout the world using the Internet. People from schoolchildren to the elderly are learning to use the web, and finding an almost endless variety of information from the convenience of their homes or places of work. Businesses, government, organizations and even ordinary individuals are making information available on the web, to the degree that it is now the expectation that anything worth knowing about is available somewhere on the web.
Early communications media, whether for human voices or for digital data, have generally relied on fixed communications stations. But as the need to communicate information has grown, it has become manifestly desirable to enable communications with mobile communications devices. Mobile communications can involve communications between an isolated pair of mobile devices, but in particular it has been desirable to enable a mobile communications device to link to a large network which couples it, by a series of wired and/or wireless links, to many other devices (either mobile or fixed). One outstanding example of such communications is the a mobile cell phone, which is coupled to a worldwide telephone network by which it is possible to place or receive a telephone call with another telephone, either mobile or fixed, nearly anywhere in the world. Another outstanding example is a laptop, palmtop or other mobile digital computing device, connected via a wireless connection (e.g., an IEEE 802.11 protocol connection) to the Internet, whereby it may send and receive data over the Internet from any other device in the world coupled to the Internet.
Wireless Internet, cell phones, and other wireless network connections have generally followed a common paradigm. Due to greater bandwidth, the backbone of the network is generally a fixed tangible transmission medium, such as copper wires, fiber-optic cable, and so forth, running between fixed routers or other network nodes. Multiple wireless transceiver stations in fixed, dispersed locations are coupled to the tangible transmission medium network. Each wireless transceiver station has a respective range for communicating with mobile wireless devices. To connect to the network, a mobile wireless device determines the presence of a wireless transceiver station within range and establishes a connection with that wireless transceiver station, according to a pre-established protocol. Ideally, the wireless transceiver stations are located to provide coverage over a desired area, i.e., so that a mobile device is within range of at least one such transceiver station, wherever the mobile device is currently located within the desired area of coverage.
For a certain class of communications protocols, the mobile device (referred to as a client) discovers an appropriate wireless transceiver station and establishes a connection with that particular station (acting as a server). As part of the protocol, the client addresses communications to the particular wireless transceiver station with which the connection was established. Once the connection is established, the client is free to move about within the range of the station's transceiver, and the connection will be maintained. However, if the client moves out of range of the transceiver station with which it established a connection, the connection may be dropped, notwithstanding that the device may be within range of a different transceiver station, unless the applicable protocol and the wireless device. If the connection is dropped, the client must then re-establish a new connection with the new transceiver station.
This problem of losing of a connection as a mobile device moves out of range is well known in the cell phone industry, wherein certain special protocols exist to hand off a connection from one cell phone tower to another as a cell phone moves out of range of the tower with which the connection was originally made. In the case of an IEEE 802.11 protocol and certain similar protocols, the range of the transceiver station is typically much shorter, and hence the restriction on mobility is potentially more severe. However, this is accepted in most cases because the mobile device is often used in a stationary manner. I.e., a laptop computer may be carried around from one location to another, but in use it is typically placed on a desk, and remains at that location during a particular communications session. Thus, the relatively short range of the transceiver station is often not a problem. When a user wishes to initiate a session, he finds a transceiver station within range, and stays at that location for the duration of the session.
Notwithstanding these “typical” behaviors, there are numerous reasons, not always fully appreciated, why it would be desirable to provide a continuous wireless connection which is not limited to the range of any particular wireless transceiver station. In the first place, dropped connections are an annoyance, even if they don't happen often enough to make communications impossible or impractical. Secondly, while digital computing devices using relatively short range IEEE 802.11 or similar wireless connections are often operated in a stationary manner, there are not always stationary, and it is sometimes desirable to maintain the connection while the digital computing device is moving. But even more significantly, extending the range of wireless transceiver stations to reduce the frequency of dropped connections has unwanted side-effects. It means either greater overlap of coverage or a larger number of devices supported by each transceiver station, or both. These circumstances can limit the bandwidth supported by the network, because each wireless transceiver station must support a large area, i.e., one having many devices within it. Put another way, a larger number of transceiver stations, each having a smaller coverage area, can generally support a higher communications bandwidth than a smaller number of stations each having a larger coverage area.
As the number of mobile communications devices increases, and the volume of data transmitted to and from mobile devices increases, there is a need to find improved methods of communicating with mobile devices which support greater bandwidths of data transfer and greater freedom of movement for people and devices.